I want to make an I2C master controller board/shield which can work with the atmega168/328/640/644.It must be compatible with the $50(168), Axon's and Arduino's (wide group of users). Support 3.3v and 5vControl servo's (slave boards) and sensors, etc

Its design will use external resistors and communicate at 100kbps (Standard mode) and 400kbps (Fastmode)Perhaps a USB / Uart. The board/Shield will have 8-16 pins for slave devices.